The invention relates to an airplane door window for a passenger plane, with an outer pane, an inner pane, an intermediate pane situated parallel between the outer pane and inner pane and designed as an optical lens body, and a continuous window seal.
Such airplane door windows are known from EP 1 188 664 A2, for example. Disclosed therein is an airplane door window with an outer pane and an inner pane, which are sealed airtight relative to a window frame at the support points, and an intermediate pane arranged in between parallel to the outer pane and inner pane. The intermediate pane is there designed as an optical lens body in the form of a Fresnel lens. Such an airplane door window with corresponding visual aids is necessary, since safety regulations prescribe that, after an emergency landing, the impact area for emergency slides, the staircase joined to the aircraft before opening the airplane door, or a board finger be visible to passengers.
A Fresnel lens arranged on the airplane door window is helpful for this purpose, since the airplane door window usually lies in a fuselage section above the centerline bend in the aircraft fuselage, so that it is directed upward, and outside areas below the airplane fuselage can only be viewed with difficulty form inside. A Fresnel lens facilitates the view of lower-lying areas, wherein the Fresnel lens is distinctly more lightweight than prisms, complicated mirror mechanisms or complete lens systems also known in prior art for implementing the mentioned safety regulations.
In the known airplane door window, there may be cases where cabin pressure may place a burden on the Fresnel lens designed to cover the most possible surface between the usually circular outer pane and circular inner pane, impairing the integrity of the lens and lens attachment underneath. In addition, the circular, bull's eye design of known airplane door windows often limits the visual field.